The number to pay attention to over at 538.com is the chance of a brokered Democratic convention.  Nate Silver has built a model that shows the likelihood of no candidate having a majority of delegates in Milwaukee four and a half months from now.

Less than three weeks ago, on February 10, there was just a 25% chance of a brokered convention.  At the time, Sanders had a 48% chance — even money, really — of having a majority of delegates and winning on the first ballot.

Today, Sanders's chances of a majority are down to one in three, and after failing spectacularly with black voters in South Carolina, those chances will go down even more.  Right now there's a 52% chance of a brokered convention, and I bet that gets a boost after the results from South Carolina are factored in.

A brokered convention means a broken Democratic party.  Nobody will want to back down, and there will be days and days of acrimony and spectacle made just for TV and Twitter and YouTube.  The media would go wild.  It would be an absolute debacle.

Normally, national political conventions are just a boring rubber stamp, along with endless speeches.  Milwaukee 2020 could be one for the ages.

Six weeks later, at the end of August, Trump will be coronated in Charlotte, North Carolina.  It won't be a political convention; it will be a giant Tribute to Trump extravaganza. A unified and energized Republican party will emerge to rally behind the president against a divided and dispirited Democratic party.

That's what a brokered Democratic convention would mean, and that's what to watch for.

In 1964 Fritz Pettyjohn snuck into the Republican convention at the Cow Palace in San Francisco to hear Senator Everett Dirksen of Illinois nominate Barry Goldwater for president.